Method and apparatus for steering twin hulled vessels



May 12, 1976 E. G. TATTERSALL 3,511,204

METHOD AND APPARATUS FOR STEERING TWIN HULLED VESSELS Filed Nov. 27,1968 2 Sheets-Sheet L FIG] BY W

y 1970 E. G. TATTERSALL 3,511,204

METHOD AND APPARATUS FOR STEERING TWIN HULL-ED VESSELS Filed Nov. 27,1968 2 Sheets-Sheet 2 FIG] ,W- 3? A. I1 Y Q 1 20 20 1/ 23 Wgm 7M 3r WUnited States Patent O 3,511,204 METHOD AND APPARATUS FOR STEERING TWINHULLED VESSELS Edward Gunston Tattersall, Hythe, Southampton, England,assignor to Hovermarine Limited, London, England, a corporation of theUnited Kingdom Continuation-impart of application Ser. No. 672,067,

Oct. 2, 1967. This application Nov. 27, 1968, Ser.

No. 779,349 Claims priority, application Great Britain, Dec. 23, 1967,58,571/ 67 Int. Cl. B63h 25/06 US. Cl. 114-163 13 Claims ABSTRACT OF THEDISCLOSURE A twin-hulled marine craft, for example, a sidewallair-cushion craft, is steered by a pair of rudders, one rudder disposedbeneath each hull. The rudders are inclined outwardly so that when thecraft executes a turn a force couple is generated which tends to bankthe craft into the turn.

This is a continuation-in-part application of application Ser. No.672,067, filed Oct. 2, 1967, now abandoned.

This invention relates to methods of apparatus for steering twin-hulledmarine craft.

Application Ser. No. 672,067 disclosed a twin-hulled marine craft havinga plurality of control surfaces in the form of rudders disposedlaterally beneath the hulls of the craft in a symmetrical arrangement,each of the surfaces being disposed in a plane inclined to the vertical.

The invention disclosed by application Ser. No. 672,067 has particularapplication to a sidewall gas-cushion craft or vehicle, that is to say,to a vehicle for travelling over water and which, in operation, issupported above the water by a cushion of compressed gas, for example,air formed between the vehicle body and the surface of the water. Thesides of the vehicle-supporting cushion are contained by a pair oflongitudinal hull structures or sidewalls extending lengthwise along thesides of the vehicle body and depending therefrom to dip into the waterand effect a cushion seal. In this application the control surfacescomprise a pair of rudders, each rudder being disposed beneath asidewall.

According to one aspect of the invention, a marine craft is providedwith craft steering means comprising a pair of steering control membersmounted beneath the craft so as to be symmetrical with respect to thelongitudinal axis of the craft and so as to be disposed in planesinclined to the vertical, and means for pivoting each control surfaceabout a substantially vertical axis.

According to another aspect of the invention, a marine craft comprises apair of laterally-spaced hull structures, each hull structure havinginner and outer side surfaces and a bottom surface wherein the innersurface extends downwardly below the outer side surface, and the bottomsurface presents a downwardly and inwardly sloping face and means forsteering the craft, said means comprising a steering control membermounted beneath each hull structure in a plane inclined to the verticalwhereby the inclined planes intersect at a point above the controlmembers so as to include an acute angle therebetween.

The craft may further comprise a pair of longitudinal hull structuresspaced apart by a central body structure, wherein the steering controlmembers are disposed beneath the hull structures and are pivoted byshafts extending upwardly through the hull structures.

The craft may be provided with means for forming a craft-supportingcushion of pressurised gas beneath the body structure, the sides of saidcushion being contained by the hull structures. The craft then comprisesa sidewall gas-cushion vehicle.

An embodiment of the invention according to its various aspects will nowbe described by way of example with reference to the accompanyingdrawings wherein:

FIG. 1 is a side view of a sidewall gas-cushion vehicle,

FIG. 2 is a rear view of part of the vehicle and to a slightly enlargedscale,

FIG. 3 is another rear view of the vehicle, this time in broken form andto a further enlarged scale,

FIG. 4 is a diagrammatic rear-end view of the vehicle and illustratesthe forces created by the steering control members,

FIG. 5 is a view generally similar to FIG. 4 but illustrating adifferent form of sidewall of the vehicle, and

FIGS. 6 and 7 are diagrammatic plan views of the rear end of the vehicleand illustrate the steering control members in both neutral and steeringpositions.

With reference to FIG. 1 to 3, a sidewall gas-cushion vehicle 1 travelsover a water surface 2 and is supported thereover by a cushion 3 (notFIG. 1) of pressurised air formed between the vehicle body 4 and thewater 2. The sides of the vehicle-supporting air-cushion 3 are containedby a spaced pair of longitudinal hulls or sidewalls 5 of solidconstruction extending lengthwise along the sides of the vehicle body 4and depending therefrom to dip into the Water 2 and effect a seal. Thebow end of the cushion 3 is contained by a multi-part flexible wall orskirt 6 and the rear end thereof by a one-piece flexible skirt in theform of an inflated bag 7.

The air forming the cushion 3 is drawn in from the atmosphere, throughside intakes 8, by a compressor 9 driven by a variablespeed engine 10.The pressurised air is discharged to the space (the cushion space)occupied by the cushion 3 by a duct 11 and the bag 7 is inflated by airtapped off the duct 11 by a duct 12. The vehicle 1 is propelled bywater-screw propellers 13 rotated by inclined shafts 14 located in thesidewalls 5. The shafts are driven by variable-speed engine and gearboxunits 15. The vehicle 1 is steered by a pair of control surfaces orrudders arranged to work in unison. Each rudder 20 is of tapered sectionand is disposed laterally beneath the vehicle in a substantiallysymmetrical arrangement, the upper parts of each of the rudders 20 beinginclined at about Lo. between 55 and about a substantially horizontalaxis 21 extending in a direction substantially parallel to thelongitudinal axis 27 FIGS. 2 and 3, only) of the vehicle. Thus, eachrudder 20 is disposed in a plane inclined to the vertical. Each rudder20 is pivoted about a substantially vertical axis 25. The inclinedplanes of the rudders 20 intersect at a point well above the rudders 20and together define an acute angle.

Each rudder 20 is pivoted about its axis 25 by a shaft 23 which is bentat a point adjacent the upper edge of the nudder 20 so that itpenetrates the bottom edge of the associated sidewall 5 to extendupwardly therefrom in a substantially vertical direction where itconnects with electrically-operated tiller apparatus 24 under thecontrol, through electrical signal lines (not shown), of the pilot ofthe vehicle.

The axes of the shafts 23 thus change in direction from lying in theplaces of the rudders 20 at points adjacent the rudders 23 to beingcoaxial with the axes 25. Accordingly, although the rudders 20 areinclined downwardly and outwardly at the required angles, the majorparts of the shafts 23 extend upwardly through the sidewalls 5 with amainly vertical component of direction.

The arrangement demands the provision of only one seal (the seal 26 ofFIG. 3) for each shaft 23 and allows the tiller apparatus 24 to bedisposed immediately above the sidewalls 5 and in outboard positionswhere they are not inconveniently placed.

With reference to FIG. 4, the inclined rudder arrangement results in thecreation of horizontal (X) and vertical (Y) components of force whichact in opposite directions and thereby set up a couple Y.d about thecentral longitudinal axis 27 of the vehicle 1, d being the lateraldistance separating the rudders 20. This couple acts, when the vehicleexecutes a turn to starboard, as indicated by the arrow 30, to bank thevehicle into the turn. This banking effect is a desirable controlfeature. The hull structure side force exerted on the water is indicatedby the arrows 36.

In the arrangement shown in FIG. 5, each hull structure has inner andouter side surfaces 31, 32 disposed substantially parallel to eachother. The inner side surface 31 of the hull structure 5 extendsdownwardly below the outer side surface 32 thereof. Each hull structure5 also has a bottom surface 33 the whole of which presents a downwardlyand inwardly sloping face (disposed at substantially 45 to thehorizontal) extending between the lower edges of the inner and outerside surfaces 31, 32.

In operation, as the craft banks in during a turn, water pressure actingnormal to the inclined bottom surface 33 of the upgoing hull structure5, as indicated by the arrows 34, assists the banking in moment by anupward component of thrust. Water pressure does not generate asignificant upward component of thrust on the downgoing hull structure 5due to the turbulence created by sideslip of the craft.

If desired, the knife-edges defined by the converging surfaces 31 and 33can be cut back at the horizontal lines indicated at 35 so that thebottom surfaces 33 each presents an inner, horizontal face as well as anouter downwardly and inwardly sloping face. This modification eases theproblem of sealing the propeller shafts 14 (FIG. 1) to the hulls 5.

FIGS. 6 and 7 show, respectively, the relative positions of the rudders23 in the neutral (FIG. 6) position and when the vehicle 1 is turning to.port (FIG. 7), as indicated by the arrow 30.

As shown in FIG. 3, the inner and outer side surfaces of a hullstructure 5 may converge slightly in a downward direction.

I claim:

1. A marine craft provided with craft steering means comprising a pairof steering control members mounted beneath the craft so as to besymmetrical with respect to the longitudinal axis of the craft and so tobe disposed in planes inclined to the vertical, and means for pivotingeach control member about a substantially vertical axis.

2. A craft as claimed in claim 1 comprising a pair of longitudinal hullstructures spaced apart by a central body structure wherein the steeringcontrol members are disposed beneath the hull structures and whereinsaid means for pivoting the control members comprise shafts extendingupwardly through the hull structures.

3. A craft as claimed in claim I provided with means for forming acraft-supporting cushion of pressurised gas beneath the body structure,the sides of said cushion being contained by the hull structures.

4. A craft as claimed in claim 3 wherein the control members arerespectively disposed in planes whereby the upper parts of the controlmembers are disposed at about 60 to the vertical.

5. A craft as claimed in claim 2 wherein each hull structure has innerand outer side surfaces and a bottom surface, the inner side surfaceextending downwardly below the outer side surface and the bottom surfacepresenting a downwardly and inwardly sloping face.

6. A craft as claimed in claim 5 wherein each bottom surface presents ahorizontal face as well as a sloping face.

7. A craft as claimed in claim 5 wherein the whole of each of saidbottom surfaces is disposed at substantially 4 45 to the horizontal.

8. A craft as claimed in claim 5 wherein the inner and outer sidesurfaces are disposed substantially parallel to each other.

9. A marine craft comprising a pair of laterally-spaced hull structures,each hull structure having inner and outer side sufaces and a bottomsurface wherein the inner surface extends downwardly below the outerside surface, and the bottom surface presents a downwardly and inwardlysloping face and means for steering the craft, said means comprising asteering control member mounted beneath each hull structure in a planeinclined to the vertical whereby the inclined planes of the controlmembers intersect at a point above the control members so as to includean acute angle therebetween.

10. A marine craft as claimed in claim 9 provided with a central bodystructure extending between the hull structures and with means forforming a craft-supporting cushion of pressurised gas beneath thecentral body structure, the sides of said cushion being contained by thehull structures.

11. A method of steering a twin-hulled marine craft comprising mountinga rudder control surface beneath each hull structure of the craft, thecontrol surfaces being disposed laterally in a symmetrical arrangementbeneath the craft, wherein the control surfaces disposed respectively oneach side of the central fore and aft axis of the craft are respectivelydisposed in planes inclined to the vertical whereby the respectiveplanes intersect one another above the level of the control surfaces soas to include an acute angle therebetween, and causing pivotaldeflection of the control surfaces about subtantially vertical axes soas to turn the craft and so as to produce a vertical couple acting aboutthe central fore and aft axis of the craft whereby, when executing theturn, the craft is banked into the turn.

12. A marine craft as claimed in claim 9 wherein each bottom surfacepresents a horizontal face a well as a downwardly and inwardly slopingface.

13. A marine craft comprising a pair of longitudinal hull structuresspaced apart by a central body structure, craft steering meanscomprising a pair of rudders mounted beneath the craft so as to besymmetrical with respect to the longitudinal axis of the craft and so asto be disposed in planes inclined to the vertical, whereby the inclinedplanes of the rudders intersect at a point above the rudders so as toinclude an acute angle therebetween, means for pivoting each rudderabout a substantially vertical axis and including shaft membersextending upwardly through the hull structures, means for forming acraft supporting cushion of pressurised gas beneath the body structure,front and rear flexible skirt means extending between the front and rearends of the hull structures respectively so as to contain the front andrear ends of said cushion, said rear flexible skirt means being ofhollow, inflatable construction, means for supplying inflation gas tosaid rear flexible skirt means from within the craft, and craftpropulsion means carried by the hull structures, each hull structurehaving an outer surface, an inner surface which extends downwardly belowthe outer surface and a bottom surface which extends downwardly andinwardly from the outer surface and then horizontally and inwardly tothe inner surface.

References Cited UNITED STATES PATENTS 360,488 4/1887 Sweeney 114-163344,679 6/1886 Thornycroft 1l4-l63 2,263,529 11/1941 Dow 114-163 ANDREWH. FARRELL, Primary Examiner

